From: Kees Cook keescook@chromium.org
commit ee7998c50c2697737c6530431709f77c852bf0d6 upstream.
The add_device_randomness() function would ignore incoming bytes if the crng wasn't ready. This additionally makes sure to make an early enough call to add_latent_entropy() to influence the initial stack canary, which is especially important on non-x86 systems where it stays the same through the life of the boot.
Link: http://lkml.kernel.org/r/20170626233038.GA48751@beast Signed-off-by: Kees Cook keescook@chromium.org Cc: "Theodore Ts'o" tytso@mit.edu Cc: Arnd Bergmann arnd@arndb.de Cc: Greg Kroah-Hartman gregkh@linuxfoundation.org Cc: Ingo Molnar mingo@kernel.org Cc: Jessica Yu jeyu@redhat.com Cc: Steven Rostedt (VMware) rostedt@goodmis.org Cc: Viresh Kumar viresh.kumar@linaro.org Cc: Tejun Heo tj@kernel.org Cc: Prarit Bhargava prarit@redhat.com Cc: Lokesh Vutla lokeshvutla@ti.com Cc: Nicholas Piggin npiggin@gmail.com Cc: AKASHI Takahiro takahiro.akashi@linaro.org Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Linus Torvalds torvalds@linux-foundation.org Signed-off-by: Jason A. Donenfeld Jason@zx2c4.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/char/random.c | 5 +++++ init/main.c | 1 + 2 files changed, 6 insertions(+)
--- a/drivers/char/random.c +++ b/drivers/char/random.c @@ -1045,6 +1045,11 @@ void add_device_randomness(const void *b unsigned long time = random_get_entropy() ^ jiffies; unsigned long flags;
+ if (!crng_ready()) { + crng_fast_load(buf, size); + return; + } + trace_add_device_randomness(size, _RET_IP_); spin_lock_irqsave(&input_pool.lock, flags); _mix_pool_bytes(&input_pool, buf, size); --- a/init/main.c +++ b/init/main.c @@ -490,6 +490,7 @@ asmlinkage __visible void __init start_k /* * Set up the the initial canary ASAP: */ + add_latent_entropy(); boot_init_stack_canary();
cgroup_init_early();